Packaging machine with mechanism for sealing tape across the end of a carton

ABSTRACT

A carton is advanced step by step along a circular path by a rotary carrier and is sealed closed by a strip of sealing tape delivered to a sealing station by a shuttle as the carton is advanced into the sealing station. The shuttle includes an elongated tubular sheath, the tape being threaded through the sheath and held therein by a gripper. After the tape has been delivered to the sealing station, a second gripper clamps an exposed portion of the tape to the carton, the first gripper is released from the tape, and the sheath is slid reversely along the tape and back to a home station to leave the leading end portion of the tape stretched across the flaps of the open end of the carton. A sealer is then pressed against the tape and heat seals the tape to the carton flaps. Upon completion of the sealing, the second gripper is released and a cutter is advanced to sever the tape behind the trailing flap of the carton. Once the tape is cut, the sealer and cutter are retracted and the sealed carton is advanced out of the sealing station as an incident to the delivery of another carton to the sealing station.

United States Patent 1 Renner 1 Oct. 2, 1973 [75] Inventor: Robert E. Renner, Rockford, Ill.

[73] Assignee: Rexham Corporation, New York, N.Y.

[22] Filed: Mar. 15, 1971 [211 App]. No; 124,041

Primary ExaminerHarold D. Whitehead Assistant ExaminerNeil Abrams Attorney-Wolfe, Hubbard, Leydig, Voit & Osann, Ltd.

[57] ABSTRACT A carton is advanced step by step along a circular path by a rotary carrier and is sealed closed by a strip of sealing tape delivered to a sealing station by a shuttle as the carton is advanced into the sealing station. The shuttle includes an elongated tubular sheath, the tape being threaded through the sheath and held therein by a gripper. After the tape has been delivered to the sealing station, a second gripper clamps an exposed portion of the tape to the carton, the first gripper is released from the tape, and the sheath is slid reversely along the tape and back to a home station to leave the leading end portion of the tape stretched across the flaps of the open end of the carton. A sealer is then pressed against the tape and heat seals the tape to the carton flaps. Upon completion of the sealing, the second gripper is released and a cutter is advanced to sever the tape behind the trailing flap of the carton. Once the tape is cut, the sealer and cutter are retracted and the sealed carton is advanced out of the sealing station as an incident to the delivery of another carton to the sealing station.

6 Claims, 11 Drawing Figures PACKAGING MACHINE WITH MECHANISM FOR SEALING TAPE ACROSS THE END OF A CARTON BACKGROUND OF THE INVENTION This invention relates generally to a packaging machine and, more particularly, to a packaging machine of the type in which generally rectangular cartons are carried in upright positions within holders and are advanced step by step along a predetermined path to a sealing station where an open end of each carton is sealed closed by a strip of tape. A packaging machine of this general type is disclosed in Benzon-Petersen U. 8 Pat. No. 2,867,159.

SUMMARY OF THE INVENTION The primary object of the present invention is to provide a packaging machine of the above general character in which the sealing tape is uniquely delivered into position for sealing across the open end of a carton moved step by step along an arcuate path such as by a rotary carrier.

A further object is to deliver the tape to the sealing station and to stretch the tape flat across the open end of each carton for proper sealing without the tape being bent edgewise and without the sides of the tape curling or twisting. i

A more detailed object is to deliver the tape with. a novel shuttle which draws the tape along a linear path extending generally chordwise of the arcuate path and which pulls the leading end portion of the tape across the open end of the carton for sealing.

The invention also resides in the novel construction and operation of the shuttle and of various mechanisms which coact with the shuttle to effect comparatively simple and trouble-free delivery and sealing of the tape.

These and other objects and advantages of the invention will become more apparent from the following detailed description when taken in conjunction withthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary plan view of a rotary packaging machine embodying the novel features of the present invention.

FIG. 2 is a perspective view of a carton with a strip of tape sealed across each end'thereof.

FIG. 3 is an enlarged fragmentary cross-sectional view taken substantially along the line 3-3 of FIG. 1.

FIG. 4 is an enlarged fragmentary cross-sectional view taken substantially along the line 4-4 of FIG. 3.

FIG. 5 is an enlarged fragmentary cross-sectional view taken substantially along the line 5-5 of FIG. 3.

FIG. 6 is an enlarged fragmentary cross-sectional view taken substantially along the line 6-6 of FIG. 5.

FIG. 7 is an enlarged fragmentary cross-sectional view taken substantially along the line 7-7 of FIG. 6.

FIG. 8 is an enlarged fragmentary cross-sectional view taken substantially along line 8-8 of FIG. 3.

FIGS. 9 through 11 are schematic elevational views showing successive steps occurring during delivery of the tape to the sealing station and the sealing thereof to the open end of a carton.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in the drawings for purposes of illustration, the invention is embodied in a rotary packaging machine 20 operable to advance paperboard cartons 21 of rectangular cross-section step-by-step along a circular path through sealing stations 23 and 24 where the lower and upper open ends of the cartons are sealed closed by strips of sealing tape 25,. An exemplary sealed carton is shown in FIG. 2 and includes upright side and end panels 26 and 27 whose upper and lower ends are integral with hinged 'side flaps 29 and end flaps 30. The

sealing tape covers the upper and lower ends of the carton, being heat sealed to the flaps while the latter are held in outwardly or reversely folded positions as shown in FIG. 2.

In the present instance, the packaging machine 20 includes an indexable carrier or table 31 positioned above a base 33 and intermittently rotated by way of an indexing mechanism 34 and a speed reducer 35 driven, by a motor 36 as shown in FIG. 1. U-shaped carton holders 37 mounted on and spaced around the periphery of the table carry the cartons 21 in upright positions along the circular path and through the sealing stations 23 and 24. As is shown best in FIGS. 5 and 8, each holder is formed with outwardly projecting legs 39 engaging the end panels 27 and with a web 40 spanning the legs and supporting the inner side panel 26.

As the cartons are advanced along the circular path, the lower carton flaps 29 and 30 held folded reversely as shown in FIG. 2 by a stationary lower support track 41 (FIG. 5) located below the table 31. The upper carton flaps are held reversely folded by a flap holddown (not shown) similar in construction to the support track. In addition, a retaining ring (not shown) encircles the table around the open outer side of the holders 37 and prevents the cartons 21 from falling out of the holders. Thus, each carton is held within one of the holders and is carried step by step along the circular path through the first sealing station 23 where the lower tape 25 is sealed across the lower end of the carton, then through a filling station (not shown) where a product is fed into the carton through the unsealed upper end and, finally, through the second sealing station 24 where the upper end is sealed by the upper tape 25.

For brevity, only the mechanism for sealing the upper end of each carton 21 will be described in detail because the mechanism for sealing the lower end is essentially the same except for being differently oriented. As each carton is advanced into the upper sealing station 24, the strip of sealing tape 25 is delivered into position across the open upper end of the carton. Then, during the dwell period, a fluid-operated heat sealer 43 (FIG. 3) is actuated to seal the strip of tape across the upper flaps 29 and 30. To control actuation of the sealer in timed relation with the advance of the cartons, a sequential timing box 44 (FIG. 1) includes a plurality of microswitches 44a which are actuated by cams 44b on a rotatable shaft 45. The latter is driven by a chain 46 leading from one end of a power shaft 47 which extends from the reducer 35. The microswitches are connected by conventional circuitry to solenoids which openand close valves at the proper times to cause the sealer to first advance and then retract during each dwell period. Various other fluid-operated actuators (to be described subsequently) are controlled in essentially this same manner to perform other functions in the packaging operation in timed relation with the advance of the cartons.

As shown in FIGS. 3 and 5, the sealer 43 is mounted above the table 31 on a horizontal support plate 48 fixed to the lower sides of the horizontal legs of two spaced, inverted L-shaped support members 49 whose vertical legs are spaced outwardly of the periphery of the table and are connected at their lower ends to the base 33. The sealer includes an air actuated cylinder 50 mounted on top of the support plate with a rod 51 extending vertically therethrough to reciprocate upwardly and downwardly in response to the admission of pressure fluid into the cylinder through hoses 53. Connected to the end of the rod to reciprocate therewith is a sealing pressure adjuster box 54 which is held against lateral movement by guide posts 55 extending downwardly from the support plate and fitting within slots 56 at opposite ends of the adjuster box. A heat sealing shoe 57 with central heating elements 59 and a peripheral sealing flange 60 (FIG. 6) is held on the lower end of the adjuster box 54 by four rods 61 connected to the box.

Thus, as the cylinder rod 51 moves downwardly, the sealing shoe 57 is advanced to press the sealing flange 60 against the tape 25 and thereby sealing the latter to the upper flaps 29 and 30. Three of the flaps, both end flaps 30 and the inner side flap 29, are pressed by the shoe against the legs 39 and the web 40 of the holder 37 and thus are backed rigidly during sealing so that the tape can be sealed evenly across the top of the carton 21.

To provide support for the outer side flap 29, a pressure transmitting bar 65 (FIG. is held across the open side of the holder 37 and is flush with the top of the holder so as to hold the outer side flap from being bent downwardly as the sealing shoe 57 seals the tape 25 across the upper end of the carton 21. Herein, the pressure bar is a T-shaped member with its cross-piece extending substantially the length of the holder, as shown in FIGS. 3 and 8, and adapted to fit within notches 66 (FIG. 5) formed in the upper end of the legs 39 so that the top of the cross-piece may be positioned across the upper portion of the outer side panel 26 to close the open side of the holder and to support the outer side flap. The stem of the T is connected by a bolt 69 to the inner end of an elongated retractable arm 70.

As shown in FIG. 5, the retractable arm 70 is mounted to move generally radially of the circular path and to move into and out of the sealing station 24. For this purpose, the arm is slidably mounted through the upper end of a vertical standard 71 whose lower end is bolted to the machine base 33. The outer end of the arm is connected through a linkage 73 to the top end of a lever arm 74 which is adapted to be pivoted back and forth about a horizontal axis 75 by a rotating cam 76 and push spring 77 acting on the lower end portion of the lever arm below the base. The cam is mounted on a rotatable shaft 79 driven by a snake chain 80 acting through a sprocket 81 and a gear box 83 as shown in FIGS. 1 and 3. The chain is driven by a driven sprocket 84 connected to a main gear box 85 receiving power from the other end of the power shaft 47 of the reducer 35. Thus, rotation of the cam is timed in relationship to the advance of the cartons by the table 31.

As shown in FIG. 5, a follower 86 rotatably mounted on the lower end of the lever arm 74 is pressed into engagement with the cam by a spring-loaded push rod 87 which is pivotally connected to the lever arm adjacent its lower end. The push rod extends inwardly from the lever arm and is slidably received by an angle iron 89 mounted on the underside of the base 33. The push spring 77 is telescoped over the rod and is compressed between the outer side of the angle iron and a flanged nut 88 to push the rod outwardly and thereby press the follower against the cam 76. Thus, as the cam rotates, the follower follows the rise and fall of the cam and causes back and forth swinging of the lever arm to push and pull the pressure bar into and out of engagement with the holder 37. The bar is moved into engagement with each holder as the latter initially dwells in the sealing station 24 and thus supports the outer side flap 29 as the tape 25 is sealed across the upper end of the carton 21. After the tape has been sealed, the bar is retracted to free the holder for movement during the next advance of the table 31.

Once the tape 25 has been sealed to the carton 21, a vertically reciprocating cutter 93 (FIG. 3) severs the tape behind the trailing flap 30 and the carton then is advanced out of the sealing station 24. Herein, the cutter is mounted on the underside of the support plate 48 adjacent the upstream end of the sealer 43 and includes a pneumatic cylinder 94 activated in timed relationship with the advance of the cartons through an air hose 95 to advance a rod 96 carrying a vertically disposed cutter blade 97 with a serrated lower edge 98 for cutting the tape. Once the tape has been cut, the table 31 advances the sealed carton out of the sealing station 24 as another carton is advanced into the sealing station and another strip of tape is delivered for sealing across the upper end of the newly arrived carton.

In accordance with the primary aspect of the present invention, the tape 25 is delivered to the sealing station 24 of the above-described rotary packaging machine 20 on each advance stroke of a novel shuttle 99 (FIG. 3) mounted to move into the sealing station along a linear path extending generally chordwise of the circular path of advance of the cartons. Once the tape has been delivered, the shuttle is retracted to a home station spaced from the circular path and is slid back along a trailing web 100 (FIG. 10) of the tape prior to advance ment of the sealer 43 to seal the strip of tape to the carton 21. After being sealed to the carton, the strip is out free from the web by the cutter 93 so as to allow the carton to be advanced along the circular path by the table 31 without dragging the web through the sealing station or causing the web to bend edgewise out of alinement with the next carton arriving at the sealing station. Thus, utilization of the shuttle 99 moving chordwise of the table to feed the tape to the cartons advantageously permits the tape to be delivered and sealed to cartons being moved through any path configuration and, in particular, arcuate or circular paths such as those followed by the cartons when advanced by rotary packaging machines.

In the present instance, the shuttle 99 includes a tubular sheath 101 (FIG. 3) through which the tape 25 is threaded. The tape is stored on a supply roll 102 which is mounted adjacent the home station. Upon being drawn from the supply roll by the sheath, the web passes around idler rollers 103 and a dancer roller 104 which maintains proper tension in the web as the sheath carries the tape to the sealing stations 24. The sheath is mounted on a slide block 105 (FIGS. 3 and 8) which is slid along the linear path between the home station and the sealing station by a pneumatic cylinder 108 located at the home station. As the sheath is advanced with the slide block, a first gripper 107 (FIGS. 3 and 4) clamps the tape within the sheath with the tip 108 of the tape extending from the leading end of the sheath. As a result on the clamping, the tape is pulled along with the sheath to the sealing station as the sheath is advanced into the sealing station. At the sealing station, the tape tip is clamped to the leading upper carton flap 30 by a second gripper 109 (FIGS. 6 and 9) which presses the tape and flap against the leading leg 39 of the holder 37. This allows the first gripper to be released so that the sheath can be retracted reversely along the web 100 and out of the sealing station before the sealer 43 comes down and seals the tape across the upper end of the carton 21.

More specifically and as shown in FIGS. 3 and 8, one end 110 of the cylinder 106 is mounted by a bracket 111 on the outer side of a rectangular post 112 extending downwardly from the underside of the support plate 48. Slidable within the cylinder is a reciprocable rod -113 whose outer end is fixed to the slide block 105 by a bolt 114. Air hoses 118 connected at each end of the cylinder alternately pressurize opposite ends of the cylinder to reciprocate the rod in timed relation with the advance of the cartons 21. Thus, as the rod is reciprocated within the cylinder, the slide block and sheath are slid back and forth along the linear path and deliver the tape 25 to the sealing station 24 on each advance stroke.

To guide the slide block 105 along the linear path, two vertically spaced, elongated guide rods 116 and 117 (FIG. 3)*extend horizontally and parallel to the linear path from a fixed connection to the forward side of the rectangular post 112. The upper guide rod 116 fits within a longitudinal slot 1 19 (FIG. 4) extending across the topof the slide block. Preferably, the upper portions of the side walls'of the slot are defined by two elongated, removable bearing plates 120 bolted to the top of the slide block and positioned on either side of the slot to slidably engage the sides of the upper rod to provide removable wearing surfaces.

Advantageously; the sheath 101 as formed as an elongated, flattened tube extending longitudinally of the linear path with the underside of the sheath substantially level with the end of the flap holddown (not shown) so that, as the cartons 21 are advanced to the sealing station 24, the flaps 29 and 30 hit against the underside of the sheath as shown in FIGS. 4 and 8 and are prevented fromspringing upwardly. Also of advantage is the flattened shape of the sheath in that, as the tape is drawn across the open end of the carton, the sheath acts to prevent the sides of the tape from curling upwardly. Thus, the tape is held flat across the carton and a proper sealing of the tape is assured without danger of an edge being folded over inwardly and improperly sealed.

Herein, the sheath 101 is mounted on the inner side wall of the slide block 105 by an inwardly opening, U- shaped channel bracket 124 '(FIG. 4) bolted by its base web to the slide block. The bracket extends lengthwise along the lower edge of the inner side wall of the slide block, the sheath being welded to and parallel with the bottom side of the lower leg of the bracket as shown in FIG. 4.

To hold the tape within the sheath 101 as the latter is advanced, the first gripper 107 is mounted on the upper leg of the U-shaped channel bracket 124(FIG.

4) and includes a pneumatic cylinder 125 with a plunger rod 126 having a capped end 127. One end of the cylinder is threaded and telescoped through a hole 129 in the upper leg ofthe bracket with the body of the cylinder resting on and extending upwardly from the upper leg. A nut 130 threaded over the one end of the cylinder engages the bottom surface of the upper leg to securely mount the first gripper for bodily movement with the slide block 105. Air is introduced into the cylinder to move the rod 126 in timed relation with the movement of the sheath 101 through an air hose 131. As the rod 126 moves downwardly, the capped end 127 advances through an opening 133 in the lower leg of the bracket and a slot 134 in the upper wall of the sheath 101 to press the tape web 100 against the lower wall of the sheath thereby holding the tape for movement with the sheath as the latter is advanced with the slide block.

Once the tape 25 reaches the sealing station 24, the tape tip 108 is clamped to the leading flap 30 by the second gripper 109 to hold the leading end portion of the web 100 across the open upper end of the carton 21 (see FIG. 6). As shown in FIGS. 3 and 6, the second gripper includes a vertically disposed pneumatic cylinder 135 which is mounted adjacent the forward side of the sealer 43 at the sealing station 24, the cylinder being supported by a leg 136 depending from the underside of the forward end of the support plate 48. Connected to the lower end of the leg is a bracket 137 which supports the cylinder by connecting to the end thereof. A reciprocable rod 139 which is slidable within the cylinder is moved downwardly upon the introduction of air into the upper end of the cylinder through a hose 140. Connected to the end of the rod is an end piece 141 (FIGS. 6 and 7) with a tip 143 offset toward the sealer 43 from the longitudinal axis of the rod to engage the tape tip 108.

Thus, as the cylinder 135 is pressurized, the rod 139 advances to press the tip 143 against the tape tip 108 and thereby clamp the latter to the leading flap 30 of the carton 21. Accordingly, the leading end portion of the tape 25 is held across the upper end of the carton when the sheath 101 is retracted and serves to prevent the flaps 29 and 30 from springing upwardly. Once the sheath 101 has reached the home station, the sealing shoe 57 is advanced to seal the tape to the flaps and the tape in then cut adjacent the trailing flap 30 before the table 31 is indexed to advance the next carton into the sealing station 24.

By way of summary of theoperation of the embodiment just described, it will be seen that the cartons 21 are carried within the holders 37 and are advanced step by step along the circular path through the sealing station 24. As the table 31 is indexed by the indexing mechanism 34, the slide block 105 is actuated to slide the sheath 101 toward the sealing station and over the flaps 29 and 30, the first gripper 107 having been previously closed so that the tape web 100 is drawn along across the flaps by the advancing sheath. During indexing of the table and advancement of the sheath, the second gripper 109 is held open and the pressure bar 65, the sealer 43 and the cutter 93 are all retracted thereby to allow the carton and sheath to move into the sealing station.

Before the table 31 stops, the second gripper 109 starts down as illustrated in FIG. 9. Once the table is stopped, the second gripper engages the tape tip 108 and clamps the latter to the leading carton flap 30 and, at about the same time, the pressure bar 65 is advanced into position beneath the flap 29. Then, the first gripper 107 is released and the sheath 101 is retracted, sliding over the web and back to the home station as indicated in FIG. 10. As soon as the sheath is moved out of the way, the sealer 43 advances to seal the tape to the flaps 29 and 30 and close the upper open end of the carton. At about the same time that the sealer advances and as the sheath rests in its home position, the first gripper is again actuated to clamp the web within the sheath.

Once the sealing shoe 57 has been pressed against the tape 25, the second gripper 109 is released and the cutter 93 comes down to sever the tape behind the trailing flap 30 as shown in FIG. 11. Next the sealer is retracted and the cutter pulled up as the pressure bar 65 is pivoted out of engagement with the holder 37. Then the table is indexed to advance the sealed carton out of the sealing station and to advance another carton into the station. After the upper end of each carton has been sealed in this fashion, both the upper and lower flaps 29 and 30 are folded inwardly across the strips of sealing tape and are glued closed as the carton is advanced through subsequent stations.

I claim:

1. A packaging machine comprising a carrier for moving cartons step by step along an arcuate path through a sealing station where a leading end portion of tape drawn from a roll is sealed across an open end of each carton when the carrier dwells between successive steps, a shuttle moveable from a home station to the sealing station along a linear path extending generally chordwise of said arcuate path, a gripper carried by the shuttle and operable to clamp the tape for movement with the shuttle as the latter is advanced from the home station to the sealing station, means in the sealing station for sealing the leading portion of the tape across the open end of the carton, means adjacent said sealing station for holding the leading end portion of the tape across the open end of the carton, means for releasing said gripper and sliding the shuttle reversely along the tape to the home station as the leading end portion of the tape is held across the open end of the carton, and cutter means adjacent the sealing station and operable to cut the leading end portion loose from the tape after sealing of the leading end portion to the carton thereby to enable further advancement of the carton along said arcuate path. 7

' 2. A packaging machine comprising a rotary carrier for moving successive cartons step by step along a circular path into a sealing station where a leading end portion of tape drawn from a roll is sealed across an open end of each carton when the carrier dwells between successive steps, a shuttle mounted for movement from a home station to the sealing station along a linear path extending generally chordwise of said circular path, said tape being threaded into said shuttle, means for moving said shuttle from said home station to said sealing station each time a carton is advanced into the sealing station, a first gripper carried by the shuttle and operable to clamp the tape for movement with the shuttle as the latter is advanced to the sealing station, a second gripper adjacent said sealing station and operable to clamp the leading end portion of the tape across the open end of the carton upon delivery of the tape to the sealing station, means for releasing the first gripper after gripping of the tape by the second gripper, mechanism operable thereafter for sliding the shuttle reversely along the tape and back to the home station, a sealer in the sealing station for sealing the leading end portion of the tape across the open end of the carton after the shuttle has returned toward the home station, means operable to move said first gripper and cause the latter to clamp the tape to the shuttle after the shuttle has returned to the home station and as the leading end portion of the tape is being sealed, means operable to release the second gripper from the leading end portion of the tape as the latter is sealed to the carton by the sealer, and a cutter adjacent the sealing station and adapted to cut the leading end portion loose from the tape held by the first gripper after sealing of the leading end portion of the tape to the carton thereby to enable further advancement of the carton along said circular path.

3. A packaging machine as defined in claim 2 wherein said shuttle includes a slide mounted to reciprocate back and forth along said linear path between said home and sealing stations, an elongated tubular sheath with open ends and having the tape threaded therethrough, said sheath extending along said linear path and being mounted on said slide for bodily movement with the slide, and said first gripper being carried by said slide and being positioned adjacent said sheath to clamp the tape to said sheath for movement therewith.

4. A packaging machine as defined in claim 3 wherein said first gripper includes a fluid-actuated plunger movable through a hole in the sheath and operable to clamp the tape against the inner side of the sheath.

5. A packaging machine as defined in claim 2 in which each carton is of generally rectangular crosssection and includes leading and trailing flaps projecting horizontally and outwardly from said open end, said carrier including a series of holders each supporting said one of said cartons in an upright position with said flaps lying against the holder, and said second gripper comprising a fluid-actuated clamp operable to press the leading end portion of the tape against the leading flap of each carton and to press the leading flap against the associated holder.

6. A packaging machine as defined in claim 2 in which each carton is of generally rectangular crosssection and includes inner and outer side flaps and leading and trailing end flaps projecting horizontally and outwardly from said open end, said carrier comprising a series of U-shaped holders each disposed in a generally horizontal plane and having an open outer side, each of said holders supporting one of said cartons in an upright position with the end flaps and the inner side flaps lying against the holder, a pressure transmitting member mounted to reciprocate into and out of said sealing station and operable when in the sealing station to close the open outer side of each holder in the sealing station and to support the outer side flaps as said sealer seals said tape across the flaps, and means operable to move said member into said sealing station each time a carton arrives in the sealing station and to move said member out of the sealing station prior to the next advance of said carton. 

1. A packaging machine comprising a carrier for moving cartons step by step along an arcuate path through a sealing station where a leading end portion of tape drawn from a roll is sealed across an open end of each carton when the carrier dwells between successive steps, a shuttle moveable from a home station to the sealing station along a linear path extending generally chordwise Of said arcuate path, a gripper carried by the shuttle and operable to clamp the tape for movement with the shuttle as the latter is advanced from the home station to the sealing station, means in the sealing station for sealing the leading portion of the tape across the open end of the carton, means adjacent said sealing station for holding the leading end portion of the tape across the open end of the carton, means for releasing said gripper and sliding the shuttle reversely along the tape to the home station as the leading end portion of the tape is held across the open end of the carton, and cutter means adjacent the sealing station and operable to cut the leading end portion loose from the tape after sealing of the leading end portion to the carton thereby to enable further advancement of the carton along said arcuate path.
 2. A packaging machine comprising a rotary carrier for moving successive cartons step by step along a circular path into a sealing station where a leading end portion of tape drawn from a roll is sealed across an open end of each carton when the carrier dwells between successive steps, a shuttle mounted for movement from a home station to the sealing station along a linear path extending generally chordwise of said circular path, said tape being threaded into said shuttle, means for moving said shuttle from said home station to said sealing station each time a carton is advanced into the sealing station, a first gripper carried by the shuttle and operable to clamp the tape for movement with the shuttle as the latter is advanced to the sealing station, a second gripper adjacent said sealing station and operable to clamp the leading end portion of the tape across the open end of the carton upon delivery of the tape to the sealing station, means for releasing the first gripper after gripping of the tape by the second gripper, mechanism operable thereafter for sliding the shuttle reversely along the tape and back to the home station, a sealer in the sealing station for sealing the leading end portion of the tape across the open end of the carton after the shuttle has returned toward the home station, means operable to move said first gripper and cause the latter to clamp the tape to the shuttle after the shuttle has returned to the home station and as the leading end portion of the tape is being sealed, means operable to release the second gripper from the leading end portion of the tape as the latter is sealed to the carton by the sealer, and a cutter adjacent the sealing station and adapted to cut the leading end portion loose from the tape held by the first gripper after sealing of the leading end portion of the tape to the carton thereby to enable further advancement of the carton along said circular path.
 3. A packaging machine as defined in claim 2 wherein said shuttle includes a slide mounted to reciprocate back and forth along said linear path between said home and sealing stations, an elongated tubular sheath with open ends and having the tape threaded therethrough, said sheath extending along said linear path and being mounted on said slide for bodily movement with the slide, and said first gripper being carried by said slide and being positioned adjacent said sheath to clamp the tape to said sheath for movement therewith.
 4. A packaging machine as defined in claim 3 wherein said first gripper includes a fluid-actuated plunger movable through a hole in the sheath and operable to clamp the tape against the inner side of the sheath.
 5. A packaging machine as defined in claim 2 in which each carton is of generally rectangular cross-section and includes leading and trailing flaps projecting horizontally and outwardly from said open end, said carrier including a series of holders each supporting said one of said cartons in an upright position with said flaps lying against the holder, and said second gripper comprising a fluid-actuated clamp operable to press the leading end portion of the tape against the leading flap of each carton and to presS the leading flap against the associated holder.
 6. A packaging machine as defined in claim 2 in which each carton is of generally rectangular cross-section and includes inner and outer side flaps and leading and trailing end flaps projecting horizontally and outwardly from said open end, said carrier comprising a series of U-shaped holders each disposed in a generally horizontal plane and having an open outer side, each of said holders supporting one of said cartons in an upright position with the end flaps and the inner side flaps lying against the holder, a pressure transmitting member mounted to reciprocate into and out of said sealing station and operable when in the sealing station to close the open outer side of each holder in the sealing station and to support the outer side flaps as said sealer seals said tape across the flaps, and means operable to move said member into said sealing station each time a carton arrives in the sealing station and to move said member out of the sealing station prior to the next advance of said carton. 